From rice to rabbits: living with saline intrusion in Ben Tre

Cai Ladd, Tarun Bisht, Jorge Salgado, Lan Nguyen and Suzanne McGowan

The Ben Tre area at the fringes of the Mekong Delta is at the forefront of climate change. At our recent Living Deltas Hub annual meeting, a team visited The Department of Agriculture and Rural Development (DARD) to find out more.

The group posing in front of the DARD building (Credit: DARD fieldtrip team)

Ben Tre, located on the south-east coastal part of the Mekong River, is one of the most climate-affected provinces in the delta. The region is facing saline intrusion due to sea level rise, reduced river flow, erratic rainfall, and land use change. In 2015, 2016, 2019 and 2020, the area experienced unprecedented hot dry weather which coincided with reduced upstream flows, reduced rainfall, high salinity intrusion and a reduction in river catfish yields of 30-50%. Understandably, DARD see salinity intrusion as a key threat to local communities, and in response have been implementing adaptive management actions and policies.

Ben Tre is especially vulnerable to saline intrusion, as the land is exposed to the sea along the four tidally-influenced river channels that intersect the province. Freshwater dilutes the rivers along the north-west. Moving south-east towards the sea, the coconuts, banana, and pomelo orchards give way to rice paddy, and then aquaculture ponds as irrigation water becomes increasingly saline. The changing environment has also meant that rice paddy can no longer support three cropping seasons, making them less profitable.

Coconut plantation in Ben Tre province (Credit: DARD fieldtrip team)

An adaptation plan for the region is a major priority for DARD to support food security and livelihoods. The plan is focusing on two main areas: changing the type of plants and animals that are cultivated and achieving the efficient use of freshwater resources. Rice farming, previously a mainstay of the region, has been replaced by coconut plantations which are better able to withstand salinity fluctuations. Shrimp farming is also increasing as aquaculture ponds are being established. Livestock rearing is also prominent across the province. A range of animals are able to tolerate higher saline conditions including ox, goat, quail and rabbit. However, there is an increasing focus on quail and rabbit production as they have far lower water needs and can easily be raised in a smaller-scale domestic situation.

The second DARD meeting of the day close to the Cong Ba Lai dam (Credit DARD fieldtrip team)

The second aspect of water resources planning concerns hard infrastructure where the overall aim is to inhibit saline intrusion from the sea whilst slowing the exit of freshwater for agriculture. The natural hydrodynamics across this area is heavily influenced by dams, sluice gates and a network of canals that supply irrigation water. Such modifications are now vital to support agro-systems in Ben Tre, though at the cost of river connectivity which is necessary for fish passage. Increasing the retention time of freshwaters can lead to stagnation and water quality issues

The Ba Lai dam constructed in 2000 (Credit: DARD fieldtrip team)

What does the future hold for Ben Tre?

More dams, such as the planned dam in the Son Ba Lai River (“the heart of Ben Tre”) could enhance water quality issues as pollutants are retained for longer. Water security requires transnational agreements to share water equitably across the catchment, and is the overarching issue faced by managers not only here in Ben Tre, but across the world’s river deltas.

Writing the blog on the way back to Can Tho (Credit: DARD fieldtrip team)